JP7724461B2 - Resin composition, prepreg, resin-coated film, resin-coated metal foil, metal-clad laminate, and wiring board - Google Patents

Description

The present invention relates to a resin composition, a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board.

As the amount of information processed increases in various electronic devices, advances in packaging technologies, such as the high integration of semiconductor devices, higher wiring density, and multi-layering, are being made. Furthermore, wiring boards used in various electronic devices are required to be high-frequency compatible, such as millimeter-wave radar boards for automotive applications. To increase signal transmission speeds, wiring boards used in various electronic devices are required to reduce loss during signal transmission, and this is especially true for high-frequency compatible wiring boards. To meet this requirement, the substrate materials used to construct the wiring board substrates used in various electronic devices are required to have low dielectric constants and dielectric dissipation factors.

As such a substrate material, for example, a PPE-containing resin composition containing PPE (polyphenylene ether), a cross-linked curable compound, and a phosphaphenanthrene derivative has been reported (Patent Document 1).

On the other hand, electronic materials used in PA (power amplifier) boards for base stations, etc., are required to have high thermal conductivity in addition to low dielectric constants and dielectric dissipation factors. To date, a resin composition for derivatives containing anisotropic magnesium oxide has been reported as a method for improving the thermal conductivity of a resin composition (Patent Document 2), while a technology using boron nitride as an inorganic filler to achieve even higher thermal conductivity has been reported (Patent Document 3 or Patent Document 4).

The boron nitride fillers described in Patent Documents 3 and 4 above certainly improve the thermal conductivity of resin compositions, but increasing the amount of boron nitride added to these resin compositions reduces their peel strength. Therefore, simply increasing the amount of boron nitride added makes it difficult to achieve both high thermal conductivity and peel strength.

JP 2015-67700 A JP 2015-168731 A JP 2013-241321 A JP 2014-208818 A

The present invention was made in consideration of these circumstances, and aims to provide a resin composition that can yield a cured product with low dielectric properties, high thermal conductivity, and excellent peel strength. The present invention also aims to provide prepregs, resin-coated films, resin-coated metal foils, metal-clad laminates, and wiring boards that are obtained using the resin composition.

After extensive investigation, the inventors discovered that the above objective could be achieved by the following configuration, and after further investigation they achieved the present invention.

In other words, a resin composition according to one embodiment of the present invention contains a polyphenylene ether compound, a curing agent capable of reacting with the polyphenylene ether compound, and an inorganic filler including a boron nitride filler, and is characterized in that the particle size distribution of the inorganic filler, as measured by a laser diffraction particle size distribution measurement method, has at least two peaks in a particle size range of 0.8 to 30.0 μm, with at least one peak in a particle size range of 0.8 to 5.0 μm and at least one peak in a particle size range of 5.0 to 30.0 μm.

FIG. 1 is a schematic cross-sectional view showing an example of a prepreg according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing an example of a wiring board according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing an example of a resin-coated film according to an embodiment of the present invention.

The following describes in detail the embodiments of the present invention, but the present invention is not limited to these.

[Resin composition]
A resin composition according to an embodiment of the present invention contains a polyphenylene ether compound, a curing agent capable of reacting with the polyphenylene ether compound, and an inorganic filler including a boron nitride filler, and is characterized in that the particle size distribution of the inorganic filler, as measured by a laser diffraction particle size distribution measurement method, has at least two peaks in a particle size range of 0.8 to 30.0 μm, with at least one peak in a particle size range of 0.8 to 5.0 μm and at least one peak in a particle size range of 5.0 to 30.0 μm.

The above-mentioned configuration allows for the production of a resin composition that produces a cured product with low dielectric properties, high thermal conductivity, and excellent peel strength. Furthermore, by using this resin composition, it is possible to provide prepregs, resin-coated films, resin-coated metal foils, metal-clad laminates, and wiring boards with excellent performance.

First, we will explain each component of the resin composition of this embodiment.

(Polyphenylene ether compound)
The polyphenylene ether compound of the present embodiment is not particularly limited, but from the viewpoint of further reducing the dielectric properties, it is preferably a modified polyphenylene ether compound. Even more preferably, it is a polyphenylene ether compound having a group represented by formula (1) or formula (2) described below. It is believed that the inclusion of such a polyphenylene ether compound results in a resin composition that can give a cured product with low dielectric properties and high heat resistance.

In formula (1), s represents an integer of 0 to 10. Z represents an arylene group. R ₁ to R ₃ are each independent. That is, R ₁ to R ₃ may be the same group or different groups. R ₁ to R ₃ represent a hydrogen atom or an alkyl group.

In addition, in formula (1), when s is 0, it indicates that Z is directly bonded to the end of the polyphenylene ether.

The arylene group represented by Z is not particularly limited. Examples of such arylene groups include monocyclic aromatic groups such as phenylene groups, and polycyclic aromatic groups in which the aromatic ring is not monocyclic but is polycyclic, such as naphthalene rings. Arylene groups also include derivatives in which the hydrogen atom bonded to the aromatic ring is substituted with a functional group such as an alkenyl group, alkynyl group, formyl group, alkylcarbonyl group, alkenylcarbonyl group, or alkynylcarbonyl group. The alkyl group is not particularly limited, and is preferably an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include methyl, ethyl, propyl, hexyl, and decyl groups.

In formula (2), _R4 represents a hydrogen atom or an alkyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

Specific preferred examples of the substituent represented by formula (1) include substituents containing a vinylbenzyl group. Examples of the substituent containing a vinylbenzyl group include substituents represented by formula (6) below. Examples of the substituent represented by formula (2) include acrylate groups and methacrylate groups.

More specifically, examples of the substituent include vinylbenzyl groups (ethenylbenzyl groups) such as p-ethenylbenzyl groups and m-ethenylbenzyl groups, vinylphenyl groups, acrylate groups, and methacrylate groups.

The polyphenylene ether compound has a polyphenylene ether chain in the molecule, and preferably has, for example, a repeating unit represented by the following formula (7) in the molecule.

In formula (7), t represents 1 to 50. R ₅ to R ₈ are each independent. That is, R ₅ to R ₈ may be the same group or different groups. R ₅ to R ₈ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. Of these, a hydrogen atom and an alkyl group are preferred.

Specific examples of the functional groups listed for R ₅ to R ₈ include the following.

The alkyl group is not particularly limited, but for example, an alkyl group having 1 to 18 carbon atoms is preferred, and an alkyl group having 1 to 10 carbon atoms is more preferred. Specific examples include methyl, ethyl, propyl, hexyl, and decyl groups.

The alkenyl group is not particularly limited, but is preferably an alkenyl group having 2 to 18 carbon atoms, and more preferably an alkenyl group having 2 to 10 carbon atoms. Specific examples include vinyl groups, allyl groups, and 3-butenyl groups.

The alkynyl group is not particularly limited, but for example, an alkynyl group having 2 to 18 carbon atoms is preferred, and an alkynyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an ethynyl group and a prop-2-yn-1-yl group (propargyl group).

The alkylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkyl group, but for example, an alkylcarbonyl group having 2 to 18 carbon atoms is preferred, and an alkylcarbonyl group having 2 to 10 carbon atoms is more preferred. Specific examples include an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pivaloyl group, a hexanoyl group, an octanoyl group, and a cyclohexylcarbonyl group.

The alkenylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkenyl group, but for example, an alkenylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkenylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include an acryloyl group, a methacryloyl group, and a crotonoyl group.

The alkynylcarbonyl group is not particularly limited as long as it is a carbonyl group substituted with an alkynyl group, but for example, an alkynylcarbonyl group having 3 to 18 carbon atoms is preferred, and an alkynylcarbonyl group having 3 to 10 carbon atoms is more preferred. Specific examples include a propioloyl group.

The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polyphenylene ether compound are not particularly limited. Specifically, they are preferably 500 to 5,000, more preferably 800 to 4,000, and even more preferably 1,000 to 3,000. The weight-average molecular weight and number-average molecular weight may be measured using a common molecular weight measurement method, specifically, values measured using gel permeation chromatography (GPC), etc. Furthermore, when the polyphenylene ether compound has a repeating unit represented by formula (11) in its molecule, t is preferably a value such that the weight-average molecular weight and number-average molecular weight of the polyphenylene ether compound fall within the above ranges. Specifically, t is preferably 1 to 50.

When the molecular weight of the polyphenylene ether compound is within this range, it exhibits the excellent low dielectric properties of polyphenylene ether, resulting in a cured product with excellent heat resistance and excellent moldability. This is believed to be due to the following: When the weight-average molecular weight and number-average molecular weight of a typical polyphenylene ether are within this range, the cured product tends to have reduced heat resistance due to its relatively low molecular weight. In contrast, the polyphenylene ether compound of this embodiment has one or more unsaturated double bonds at its terminals, which is believed to result in a cured product with sufficiently high heat resistance. Furthermore, when the molecular weight of the polyphenylene ether compound is within this range, the relatively low molecular weight is believed to result in excellent moldability. Therefore, it is believed that such a polyphenylene ether compound not only results in a cured product with excellent heat resistance but also excellent moldability.

The average number of the substituents (number of terminal functional groups) at the molecular ends per molecule of the polyphenylene ether compound is not particularly limited. Specifically, it is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1.5 to 3. If the number of terminal functional groups is too low, it tends to be difficult to obtain sufficient heat resistance of the cured product. On the other hand, if the number of terminal functional groups is too high, the reactivity may become too high, which may result in problems such as reduced shelf life and reduced fluidity of the resin composition. In other words, when such a polyphenylene ether compound is used, insufficient fluidity may cause molding defects such as the generation of voids during multilayer molding, making it difficult to obtain highly reliable printed wiring boards.

The number of terminal functional groups of a polyphenylene ether compound can be, for example, a numerical value representing the average number of the above-mentioned substituents per molecule of all modified polyphenylene ether compounds present in 1 mole of the polyphenylene ether compound. This number of terminal functional groups can be measured, for example, by measuring the number of hydroxyl groups remaining in the resulting modified polyphenylene ether compound and calculating the difference from the number of hydroxyl groups in the polyphenylene ether before modification. This difference from the number of hydroxyl groups in the polyphenylene ether before modification is the number of terminal functional groups. The number of hydroxyl groups remaining in the modified polyphenylene ether compound can be measured by adding a quaternary ammonium salt (tetraethylammonium hydroxide) that associates with hydroxyl groups to a solution of the modified polyphenylene ether compound and measuring the UV absorbance of the resulting mixed solution.

The intrinsic viscosity of the polyphenylene ether compound of this embodiment is not particularly limited. Specifically, it may be 0.03 to 0.12 dl/g, preferably 0.04 to 0.11 dl/g, and more preferably 0.06 to 0.095 dl/g. If this intrinsic viscosity is too low, the molecular weight tends to be low, making it difficult to achieve low dielectric properties such as a low dielectric constant and a low dielectric dissipation factor. Furthermore, if the intrinsic viscosity is too high, the viscosity tends to be high, sufficient fluidity cannot be achieved, and the moldability of the cured product tends to be reduced. Therefore, if the intrinsic viscosity of the polyphenylene ether compound is within the above range, excellent heat resistance and moldability of the cured product can be achieved.

The intrinsic viscosity here is the intrinsic viscosity measured in methylene chloride at 25°C. More specifically, it is the value measured, for example, using a viscometer to measure a 0.18 g/45 ml methylene chloride solution (liquid temperature 25°C). Examples of such viscometers include the AVS500 Visco System manufactured by Schott.

Examples of the polyphenylene ether compound of this embodiment include a modified polyphenylene ether compound represented by the following formula (8) and a modified polyphenylene ether compound represented by the following formula (9). Furthermore, as the polyphenylene ether compound of this embodiment, these modified polyphenylene ether compounds may be used alone, or these two types of modified polyphenylene ether compounds may be used in combination.

In formula (8) and formula (9), R ₉ to R ₁₆ and R ₁₇ to R ₂₄ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. X ₁ and X ₂ each independently represent a substituent having a carbon-carbon unsaturated double bond. A and B represent repeating units represented by the following formula (10) and formula (11), respectively. Furthermore, in formula (9), Y represents a linear, branched, or cyclic hydrocarbon having 20 or less carbon atoms.

In formula (10) and formula (11), m and n each represent an integer of 0 to 20. _{R 25} to R ₂₈ and R ₂₉ to R ₃₂ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group.

The modified polyphenylene ether compound represented by formula (8) and the modified polyphenylene ether compound represented by formula (9) are not particularly limited as long as they satisfy the above-mentioned constitution. Specifically, in formula (8) and formula (9), R ₉ to R ₁₆ and R ₁₇ to R ₂₄ are each independent as described above. That is, R ₉ to R ₁₆ and R ₁₇ to R ₂₄ may be the same group or different groups. Furthermore, R ₉ to R ₁₆ and R ₁₇ to R ₂₄ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. Among these, a hydrogen atom and an alkyl group are preferred.

In formula (10) and formula (11), m and n each preferably represent a value of 0 to 20, as described above. Furthermore, it is preferable that m and n represent a numerical value such that the sum of m and n is 1 to 30. Therefore, it is more preferable that m represents a value of 0 to 20, n represents a value of 0 to 20, and the sum of m and n represents a value of 1 to 30. Furthermore, R ₂₅ to R ₂₈ and R ₂₉ to R ₃₂ are each independent. That is, R ₂₅ to R ₂₈ and R ₂₉ to R ₃₂ may be the same group or different groups. Furthermore, R ₂₅ to R ₂₈ and R ₂₉ to R ₃₂ represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a formyl group, an alkylcarbonyl group, an alkenylcarbonyl group, or an alkynylcarbonyl group. Among these, a hydrogen atom and an alkyl group are preferred.

R ₉ to R ₃₂ are the same as R ₅ to R ₈ in the above formula (7).

In the formula (9), Y is, as described above, a linear, branched, or cyclic hydrocarbon having 20 or fewer carbon atoms. Examples of Y include groups represented by the following formula (12):

In the formula (12), _R33 and _R34 each independently represent a hydrogen atom or an alkyl group. Examples of the alkyl group include a methyl group. Examples of the group represented by the formula (12) include a methylene group, a methylmethylene group, and a dimethylmethylene group. Among these, a dimethylmethylene group is preferred.

In the formula (8) and the formula (9), _X1 and _X2 are each independently a substituent having a carbon-carbon unsaturated double bond. There are no particular limitations on the substituents _X1 and _X2 , as long as they are substituents having a carbon-carbon unsaturated double bond. Examples of the substituents _X1 and _X2 include the substituents represented by the formula (1) above and the substituents represented by the formula (2) above. In the modified polyphenylene ether compound represented by the formula (8) and the modified polyphenylene ether compound represented by the formula (9), _X1 and _X2 may be the same substituent or different substituents.

More specific examples of modified polyphenylene ether compounds represented by formula (8) include modified polyphenylene ether compounds represented by formula (13) below.

More specific examples of modified polyphenylene ether compounds represented by formula (9) include modified polyphenylene ether compounds represented by formula (14) below and modified polyphenylene ether compounds represented by formula (15) below.

In the above formulas (13) to (15), m and n are the same as m and n in the above formulas (10) and (11). In addition, in the above formulas (13) and (14), R ₁ to R ₃ , p and Z are the same as R ₁ to R ₃ , s and Z in the above formula (1), respectively. In addition, in the above formulas (14) and (15), Y is the same as Y in the above formula (9). In addition, in the above formula (14), R ₄ is the same as R ₄ in the above formula (2).

The method for synthesizing the polyphenylene ether compound used in this embodiment is not particularly limited, as long as it is possible to synthesize a polyphenylene ether compound terminally modified with a group represented by formula (1) and/or formula (2). Specific examples include a method of reacting polyphenylene ether with a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded.

Examples of compounds in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom include compounds in which a substituent represented by the formulas (1), (2), and (6) is bonded to a halogen atom. Specific examples of the halogen atom include chlorine, bromine, iodine, and fluorine atoms, with chlorine being preferred. More specific examples of compounds in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom include p-chloromethylstyrene and m-chloromethylstyrene.

The polyphenylene ether raw material is not particularly limited as long as it can ultimately be used to synthesize the desired modified polyphenylene ether compound. Specific examples include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a difunctional phenol and a trifunctional phenol, and compounds whose main component is polyphenylene ether, such as poly(2,6-dimethyl-1,4-phenylene oxide). A bifunctional phenol is a phenolic compound having two phenolic hydroxyl groups per molecule, such as tetramethylbisphenol A. A trifunctional phenol is a phenolic compound having three phenolic hydroxyl groups per molecule.

The polyphenylene ether compound of this embodiment can be synthesized by the method described above. Specifically, the polyphenylene ether described above and a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded are dissolved in a solvent and stirred. This causes the polyphenylene ether to react with the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded, thereby producing the polyphenylene ether compound used in this embodiment.

It is preferable to carry out the reaction in the presence of an alkali metal hydroxide. This is thought to allow the reaction to proceed smoothly. This is thought to be because the alkali metal hydroxide functions as a dehydrohalogenation agent, specifically, a dehydrochlorination agent. That is, the alkali metal hydroxide eliminates hydrogen halide from the phenol group of the polyphenylene ether and a compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded. In this way, the substituent having a carbon-carbon unsaturated double bond is thought to bond to the oxygen atom of the phenol group in place of the hydrogen atom of the phenol group of the polyphenylene ether.

The alkali metal hydroxide is not particularly limited as long as it can function as a dehalogenating agent, but examples include sodium hydroxide. Furthermore, alkali metal hydroxides are typically used in the form of an aqueous solution, specifically, an aqueous sodium hydroxide solution.

Reaction conditions such as reaction time and reaction temperature vary depending on the compound in which a substituent having a carbon-carbon unsaturated double bond is bonded to a halogen atom, and are not particularly limited as long as the conditions are such that the above-described reaction proceeds favorably. Specifically, the reaction temperature is preferably room temperature to 100°C, and more preferably 30 to 100°C. The reaction time is preferably 0.5 to 20 hours, and more preferably 0.5 to 10 hours.

The solvent used during the reaction is not particularly limited, as long as it can dissolve the polyphenylene ether and the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded, and does not inhibit the reaction between the polyphenylene ether and the compound in which a substituent having a carbon-carbon unsaturated double bond and a halogen atom are bonded. Specific examples include toluene.

The above reaction is preferably carried out in the presence of not only an alkali metal hydroxide but also a phase transfer catalyst. In other words, the above reaction is preferably carried out in the presence of both an alkali metal hydroxide and a phase transfer catalyst. This is believed to facilitate the reaction. This is believed to be due to the following: A phase transfer catalyst has the ability to incorporate alkali metal hydroxide, is soluble in both polar solvents such as water and nonpolar solvents such as organic solvents, and is capable of transferring between these phases. Specifically, if aqueous sodium hydroxide is used as the alkali metal hydroxide and an organic solvent, such as toluene, that is incompatible with water, is used as the solvent, even when the aqueous sodium hydroxide is added dropwise to the solvent being used for the reaction, the solvent and the aqueous sodium hydroxide will separate, and the sodium hydroxide will not easily migrate to the solvent. This is believed to make it difficult for the aqueous sodium hydroxide added as the alkali metal hydroxide to contribute to promoting the reaction. On the other hand, when the reaction is carried out in the presence of an alkali metal hydroxide and a phase transfer catalyst, the alkali metal hydroxide is transferred to the solvent while being incorporated into the phase transfer catalyst, and the aqueous sodium hydroxide solution is thought to contribute more to promoting the reaction. Therefore, when the reaction is carried out in the presence of an alkali metal hydroxide and a phase transfer catalyst, the reaction is thought to proceed more smoothly.

The phase transfer catalyst is not particularly limited, but examples include quaternary ammonium salts such as tetra-n-butylammonium bromide.

The resin composition used in this embodiment preferably contains the modified polyphenylene ether compound obtained as described above as the polyphenylene ether compound.

(hardening agent)
The resin composition of the present embodiment further contains a curing agent capable of reacting with the polyphenylene ether compound.

The curing agent is not particularly limited as long as it can react with the polyphenylene ether compound to cure the resin composition containing the polyphenylene ether compound. Examples of the curing agent include a curing agent having at least one functional group in the molecule that contributes to the reaction with the polyphenylene ether compound.

Specific examples include compounds having two or more unsaturated double bonds in the molecule. More specific examples include styrene derivatives, compounds having an acryloyl group in the molecule, compounds having a methacryloyl group in the molecule, compounds having a vinyl group in the molecule, compounds having an allyl group in the molecule, compounds having a maleimide group in the molecule, compounds having an acenaphthylene structure in the molecule, and isocyanurate compounds having an isocyanurate group in the molecule.

Examples of the styrene derivatives include bromostyrene and dibromostyrene.

The compound having an acryloyl group in the molecule is an acrylate compound. Examples of the acrylate compound include monofunctional acrylate compounds having one acryloyl group in the molecule and polyfunctional acrylate compounds having two or more acryloyl groups in the molecule. Examples of the monofunctional acrylate compound include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of the polyfunctional acrylate compound include tricyclodecane dimethanol diacrylate.

The compound having a methacryloyl group in the molecule is a methacrylate compound. Examples of the methacrylate compound include monofunctional methacrylate compounds having one methacryloyl group in the molecule and polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compound include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compound include tricyclodecane dimethanol dimethacrylate.

The compound having a vinyl group in its molecule is a vinyl compound. Examples of the vinyl compound include monofunctional vinyl compounds (monovinyl compounds) having one vinyl group in their molecule, and polyfunctional vinyl compounds having two or more vinyl groups in their molecule. Examples of the polyfunctional vinyl compound include divinylbenzene and polybutadiene.

The compound having an allyl group in the molecule is an allyl compound. Examples of the allyl compound include monofunctional allyl compounds having one allyl group in the molecule and polyfunctional allyl compounds having two or more allyl groups in the molecule. Examples of polyfunctional allyl compounds include diallyl phthalate (DAP).

The compound having a maleimide group in the molecule is a maleimide compound. Examples of the maleimide compound include monofunctional maleimide compounds having one maleimide group in the molecule, polyfunctional maleimide compounds having two or more maleimide groups in the molecule, and modified maleimide compounds. Examples of the modified maleimide compound include modified maleimide compounds in which a portion of the molecule is modified with an amine compound, modified maleimide compounds in which a portion of the molecule is modified with a silicone compound, and modified maleimide compounds in which a portion of the molecule is modified with both an amine compound and a silicone compound.

A compound having an acenaphthylene structure in the molecule is an acenaphthylene compound. Examples of the acenaphthylene compound include acenaphthylene, alkylacenaphthylenes, halogenated acenaphthylenes, and phenylacenaphthylenes. Examples of the alkylacenaphthylenes include 1-methylacenaphthylene, 3-methylacenaphthylene, 4-methylacenaphthylene, 5-methylacenaphthylene, 1-ethylacenaphthylene, 3-ethylacenaphthylene, 4-ethylacenaphthylene, and 5-ethylacenaphthylene. Examples of the halogenated acenaphthylenes include 1-chloroacenaphthylene, 3-chloroacenaphthylene, 4-chloroacenaphthylene, 5-chloroacenaphthylene, 1-bromoacenaphthylene, 3-bromoacenaphthylene, 4-bromoacenaphthylene, and 5-bromoacenaphthylene. Examples of the phenylacenaphthylenes include 1-phenylacenaphthylene, 3-phenylacenaphthylene, 4-phenylacenaphthylene, and 5-phenylacenaphthylene. The acenaphthylene compound may be a monofunctional acenaphthylene compound having one acenaphthylene structure in the molecule, as described above, or a polyfunctional acenaphthylene compound having two or more acenaphthylene structures in the molecule.

The compound having an isocyanurate group in the molecule is an isocyanurate compound. Examples of the isocyanurate compound include compounds that further have an alkenyl group in the molecule (alkenyl isocyanurate compounds), such as triallyl isocyanurate (TAIC).

Among the above, the curing agents used in this embodiment are preferably, for example, polyfunctional acrylate compounds having two or more acryloyl groups in the molecule, polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule, polyfunctional vinyl compounds having two or more vinyl groups in the molecule, styrene derivatives, allyl compounds having allyl groups in the molecule, maleimide compounds having maleimide groups in the molecule, acenaphthylene compounds having an acenaphthylene structure in the molecule, and isocyanurate compounds having an isocyanurate group in the molecule.

The above curing agents may be used alone or in combination of two or more.

The curing agent preferably has a weight-average molecular weight of 100 to 5,000, more preferably 100 to 4,000, and even more preferably 100 to 3,000. If the curing agent's weight-average molecular weight is too low, the curing agent may be more likely to volatilize from the resin composition's blended components. Furthermore, if the curing agent's weight-average molecular weight is too high, the resin composition's varnish viscosity and melt viscosity during heat molding may become too high. Therefore, when the curing agent's weight-average molecular weight is within this range, a resin composition with superior heat resistance can be obtained. This is thought to be because the reaction with the polyphenylene ether compound allows the resin composition containing the polyphenylene ether compound to be cured appropriately. The weight-average molecular weight may be measured using a common molecular weight measurement method, specifically, a value measured using gel permeation chromatography (GPC), etc.

The average number of functional groups per molecule of the curing agent that contribute to the reaction with the polyphenylene ether compound (number of functional groups) varies depending on the weight-average molecular weight of the curing agent, but is preferably 1 to 20, and more preferably 2 to 18. If the number of functional groups is too low, it tends to be difficult to obtain sufficient heat resistance for the cured product. On the other hand, if the number of functional groups is too high, the reactivity may become too high, which may result in problems such as reduced shelf life or reduced fluidity of the resin composition.

(inorganic filler)
The resin composition according to this embodiment further includes an inorganic filler containing boron nitride. The boron nitride can be used as the inorganic filler contained in the resin composition, and is not particularly limited as long as it satisfies the particle size distribution requirements described below. Examples of boron nitride include a hexagonal normal pressure phase (h-BN) and a cubic high pressure phase (c-BN).

In the inorganic filler of this embodiment, the particle size distribution of the inorganic filler, as measured by laser diffraction particle size distribution measurement, has at least two peaks in the particle size range of 0.8 to 30.0 μm, with at least one peak in the particle size range of 0.8 to 5.0 μm and at least one peak in the particle size range of 5.0 to 30.0 μm. In other words, the inorganic filler used in this embodiment contains a mixture of relatively small and relatively large inorganic fillers, as well as inorganic fillers with at least two peak particle sizes (peak tops = maximum values). Using only small or large inorganic fillers makes it difficult to achieve both high thermal conductivity and peel strength in the cured resin composition. Furthermore, containing only small inorganic fillers tends to fail to sufficiently enhance the thermal conductivity and heat resistance of the resulting cured resin composition. Furthermore, containing only large inorganic fillers tends to reduce the moldability of the resulting resin composition.

In this specification, the particle size distribution is a value measured by particle size distribution measurement using a laser diffraction/scattering method, and can be measured, for example, using a wet particle size distribution analyzer ("SALD-2100") manufactured by Shimadzu Corporation, which is used in the examples described below. Furthermore, in this embodiment, the peak refers to the maximum value in a particle size distribution graph, and specifically, is the numerical value obtained by the maximum value in a particle size distribution graph when the horizontal axis represents particle diameter and the vertical axis represents relative particle amount (frequency).

Furthermore, it is preferable that the cumulative proportion of particles in the particle size range of 0.1 to 5.0 μm is 20 to 80%, and the cumulative proportion of particles in the particle size range of 5.0 to 150.0 μm is 20 to 80%, relative to the total particle size distribution of the inorganic filler (100%). Each of these cumulative proportions (%) is determined by calculating the cumulative value of the relative particle amount in each particle size range.

The boron nitride contained in the inorganic filler of this embodiment is identified by energy dispersive X-ray analysis (EDX analysis) of a vertical cross section of a cured resin composition of this embodiment, and more preferably, of the boron nitride particles present within an area of 50 μm on a side in SEM observation, the longest length from end to end of the boron nitride particles is 10 μm or more and 50 μm or less, in the range of 3 to 30. This has the advantage of ensuring copper foil peel strength while maintaining high thermal conductivity.

The resin composition of this embodiment may contain only the boron nitride, or may contain inorganic fillers other than the boron nitride.

When only boron nitride is contained, two or more types of boron nitride with different particle sizes are used so that the particle size distribution of the inorganic filler satisfies the above-mentioned specifications. Furthermore, when an inorganic filler other than boron nitride is contained, the particle sizes of the boron nitride and the inorganic filler other than boron nitride may be adjusted so that the particle size distribution of the inorganic filler satisfies the above-mentioned specifications.

The inorganic filler other than boron nitride is not particularly limited as long as it can be used as an inorganic filler in the resin composition. Examples of inorganic fillers other than boron nitride include metal oxides such as silica, alumina, titanium oxide, magnesium oxide, and mica; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; talc, aluminum borate, barium sulfate, aluminum nitride, silicon nitride, magnesium carbonates such as anhydrous magnesium carbonate; and calcium carbonate. Among these, preferred inorganic fillers other than boron nitride are silica, anhydrous magnesium carbonate, alumina, and silicon nitride. The silica is not particularly limited, and examples include crushed silica and silica particles, with silica particles being preferred. The magnesium carbonate is not particularly limited, but anhydrous magnesium carbonate (synthetic magnesite) is preferred.

The inorganic filler other than boron nitride may be a surface-treated or untreated inorganic filler. Examples of the surface treatment include treatment with a silane coupling agent.

Examples of the silane coupling agent include silane coupling agents having at least one functional group selected from the group consisting of a vinyl group, a styryl group, a methacryloyl group, an acryloyl group, and a phenylamino group. Specifically, the silane coupling agent includes compounds having at least one reactive functional group selected from the group consisting of a vinyl group, a styryl group, a methacryloyl group, an acryloyl group, and a phenylamino group, and further having a hydrolyzable group such as a methoxy group or an ethoxy group.

Examples of the silane coupling agent include those having a vinyl group, such as vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the silane coupling agent include those having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane. Examples of the silane coupling agent include those having a methacryloyl group, such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. Examples of the silane coupling agent include those having an acryloyl group, such as 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent include those having a phenylamino group, such as N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane.

When the inorganic filler of this embodiment contains an inorganic filler other than boron nitride, it is preferable that the content of boron nitride in the inorganic filler is 25 to 80 parts by volume per 100 parts by volume of the inorganic filler. This is believed to more reliably achieve high thermal conductivity. An even more preferable range is 30 to 70 parts by volume.

In this embodiment, the average particle size of the boron nitride and/or the average particle size of the inorganic filler other than the boron nitride is not particularly limited, as long as the particle size distribution of the inorganic filler of this embodiment satisfies the above-mentioned specifications.

In the inorganic filler of this embodiment, not only do the particle size distribution peaks described above exist in the particle size range of 0.8 to 5.0 μm and the particle size range of 5.0 to 30.0 μm, but a third peak may also exist in another particle size range. In this case, it is preferable that the third peak exists in the particle size range of 0.1 to 0.8 μm. This can be expected to have the advantage of improving thermal conductivity by dispersing the filler more uniformly in the resin component.

In a more preferred embodiment, the resin composition of this embodiment preferably contains boron nitride and silica as inorganic fillers. Furthermore, the particle size distribution of the inorganic filler containing boron nitride and silica, as measured by a laser diffraction particle size distribution measurement method, preferably has at least three peaks in the particle size range of 0.8 to 30.0 μm, with at least one peak in the particle size range of 0.8 to 5.0 μm, at least one peak in the particle size range of 5.0 to 30.0 μm, and at least one peak in the particle size range of 0.1 to 0.8 μm. In this case, the particle size distribution of the inorganic filler of this embodiment will have at least three peaks. However, it is preferable to adjust the particle size distribution by including at least two different particle sizes of boron nitride and silica. This configuration is believed to further provide the advantage of improving thermal conductivity by uniformly dispersing the highly thermally conductive filler in the resin components.

(styrene polymer)
The resin composition of the present embodiment may further contain a styrene-based polymer in addition to the components described above. The inclusion of a styrene-based polymer is considered to have the advantage of further reducing the dielectric constant of the cured resin composition.

The styrene-based polymer used in this embodiment is, for example, a polymer obtained by polymerizing a monomer containing a styrene-based monomer, and may be a styrene-based copolymer. Examples of the styrene-based copolymer include copolymers obtained by copolymerizing one or more styrene-based monomers with one or more other monomers copolymerizable with the styrene-based monomer. Examples of the styrene-based monomer include styrene, styrene derivatives, and styrene in which some of the hydrogen atoms have been substituted with substituents.

Specific styrene-based polymers that can be used include a wide range of conventionally known polymers, and are not particularly limited. Examples include polymers having a structural unit (structure derived from a styrene-based monomer) represented by the following formula (3) in the molecule.

In formula (3), R ₃₅ to R ₃₇ each independently represent a hydrogen atom or an alkyl group, and R ₃₈ represents a group selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an isopropenyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. The alkenyl group is preferably an alkenyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group.

The styrene-based polymer of this embodiment preferably contains at least one structural unit represented by the above formula (3), but may contain a combination of two or more different structural units. It also preferably contains a structure in which the structural unit represented by the above formula (3) is repeated.

Furthermore, in addition to the structural unit represented by formula (3) above, the styrene-based polymer of this embodiment may have, as other monomers copolymerizable with the styrene-based monomer, at least one of structural units represented by the following formulas (4), (17), and (18), and repeating structures in which the structural units represented by formulas (4), (17), and (18) are respectively repeated.

In the formulas (4), (17), and (18), R ₃₉ to R ₅₆ each independently represent a group selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, and an isopropenyl group. The alkyl group is not particularly limited, and is preferably, for example, an alkyl group having 1 to 18 carbon atoms, and more preferably an alkyl group having 1 to 10 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, a hexyl group, and a decyl group. The alkenyl group is preferably an alkenyl group having 1 to 10 carbon atoms. The styrene-based polymer of this embodiment preferably contains at least one structural unit represented by the formula (4), formula (17), or formula (18) above, and may contain a combination of two or more different structural units. The polymer may also contain a structure in which the structural units represented by the formula (4), formula (17), and/or formula (18) above are repeated.

More specifically, examples of the structural unit represented by formula (3) above include structural units represented by the following formulas (19) to (21), and structures in which the structural units represented by formulas (19) to (21) are respectively repeated. The styrene-based polymer of this embodiment is not particularly limited, but preferably has one or more repeating structures selected from those in which the structural units represented by formulas (19) to (21) are respectively repeated.

More specifically, examples of the structural unit represented by formula (4) above include structural units represented by the following formulas (5) and (22) to (27), and structures in which the structural units represented by formulas (22) to (27) are respectively repeated. When the styrene-based polymer of this embodiment contains the structural unit represented by formula (4) above, there are no particular limitations, but it is preferable that it has one or more repeating structures selected from the group of repeating structures in which the structural units represented by formulas (5) and (22) to (27) are respectively repeated, and it is even more preferable that it contains formula (5).

More specifically, examples of the structural unit represented by formula (17) above include structural units represented by the following formulas (28) to (29), and structures in which the structural units represented by formulas (28) to (29) are respectively repeated. When the styrene-based polymer of this embodiment contains the structural unit of formula (17) above, there are no particular limitations, but it is preferable that the polymer have one or more repeating structures selected from the group of repeating structures in which the structural units represented by formulas (28) to (29) are respectively repeated.

More specifically, examples of the structural unit represented by formula (18) above include structural units represented by the following formulas (30) to (31), and structures in which structural units represented by formulas (30) to (31) are repeated. When the styrene-based polymer of this embodiment contains the structural unit of formula (18), there are no particular limitations, but it is preferable that the polymer have one or more repeating structures selected from the group of repeating structures in which the structural units represented by formulas (30) to (31) are respectively repeated.

Preferred examples of styrene-based polymers include polymers or copolymers obtained by polymerizing or copolymerizing one or more styrene-based monomers, such as styrene, vinyltoluene, α-methylstyrene, isopropenyltoluene, divinylbenzene, and allylstyrene. More specific examples include styrene-butadiene copolymers and styrene-isobutylene copolymers. Hydrogenated styrene-based polymers are also acceptable, such as hydrogenated methylstyrene (ethylene/butylene) methylstyrene copolymers, hydrogenated methylstyrene (ethylene-ethylene/propylene) methylstyrene copolymers, hydrogenated styrene-isoprene copolymers, hydrogenated styrene-isoprene styrene copolymers, hydrogenated styrene (ethylene/butylene) styrene copolymers, and hydrogenated styrene (ethylene-ethylene/propylene) styrene copolymers.

The styrene-based polymers listed above may be used alone or in combination of two or more.

In addition to the effects described above, the inclusion of such a styrene-based polymer can also have the further effect of suppressing the moisture absorption rate of the cured resin composition, thereby preventing deterioration of electrical properties due to increased moisture absorption.

In a preferred embodiment, when the styrene-based polymer contains at least one of the structural units represented by formulas (19) to (21), the molar fraction of the structural unit is preferably approximately 10 to 70%, and more preferably 15 to 65%, of the entire polymer. This has the added advantage of maintaining compatibility with the resin, thereby maintaining uniformity of properties within the resin composition.

The polymerization form of the styrene-based polymer is not particularly limited, and may be a block copolymer, alternating copolymer, random copolymer, graft copolymer, etc. It may also be in the form of an elastomer.

The weight-average molecular weight and number-average molecular weight of the styrene-based polymer of this embodiment are preferably approximately 10,000 to 200,000, and more preferably approximately 20,000 to 150,000. Having an average molecular weight within the above range has the advantage of ensuring appropriate resin fluidity in the B-stage of the cured resin. The weight-average molecular weight and number-average molecular weight may be measured using a general molecular weight measurement method, and specific examples include values measured using gel permeation chromatography.

In a preferred embodiment, the styrene-based polymer preferably includes a styrene-isobutylene-styrene-based block copolymer (SIBS) containing a structural unit represented by the following formula (16). This has the advantage of making it possible to obtain a resin composition with high gas barrier properties and suppressing moisture absorption by the resin composition.

In formula (16), the sum of a1 and a2 is an integer between 1,000 and 60,000, b is an integer between 1,000 and 70,000, and the sum of a1, a2, and b is 10,000 to 130,000.

The method for producing the styrene-based polymer used in this embodiment is not particularly limited, but for example, as an example of a method for producing the SIBS, it can be synthesized by first polymerizing isobutylene using a living cationic polymerization method, and then adding and polymerizing styrene.

Commercially available styrene-based polymers may be used in this embodiment, such as "SIBSTAR (registered trademark) 073T," "SIBSTAR (registered trademark) 103T," and "SIBSTAR (registered trademark) 102T" manufactured by Kaneka Corporation, and "Septon V9827" manufactured by Kuraray Co., Ltd.

(Content of each ingredient)
In the resin composition of this embodiment, the content of the polyphenylene ether compound is preferably 50 to 90 parts by mass, more preferably 55 to 85 parts by mass, and even more preferably 60 to 80 parts by mass, relative to 100 parts by mass of the total of the polyphenylene ether compound and the curing agent (and the styrene-based polymer, if the styrene-based polymer is included). That is, the content of the polyphenylene ether compound is preferably 50 to 90% by mass relative to the components other than the inorganic filler in the resin composition. It is believed that if the content of the polyphenylene ether compound is within the above range, a resin composition that can produce a cured product with low dielectric properties and high heat resistance can be more reliably obtained.

The content of the curing agent is preferably 10 to 40 parts by mass, and more preferably 15 to 35 parts by mass, per 100 parts by mass of the total of the polyphenylene ether compound and the curing agent (and the styrene-based polymer, if the styrene-based polymer is included) in the resin composition. If the content of the curing agent is within the above range, the resin composition will have superior heat resistance in the cured product. This is thought to be because the curing reaction between the resin components of this embodiment and the curing agent proceeds smoothly.

The content of the inorganic filler in the resin composition of this embodiment is 20 to 60 parts by volume, based on 100 parts by volume of the total of the polyphenylene ether compound, the curing agent, and the inorganic filler (and the styrene-based polymer, if the styrene-based polymer is included). The content of the inorganic filler (filler content) is preferably 20 to 60 parts by volume, based on 100 parts by volume of the resin composition. A more preferred content is 25 to 55 parts by volume. If the content is less than 20 parts by volume, sufficient thermal conductivity cannot be obtained, while if it exceeds 60 parts by volume, moldability is thought to be impaired. In other words, if the content of the inorganic filler is within the above range, a cured product with high thermal conductivity and a resin composition with excellent moldability can be obtained.

Furthermore, the content of the boron nitride in the resin composition of this embodiment is preferably 15 to 30 parts by volume per 100 parts by volume of the total of the resin components (the polyphenylene ether compound, the curing agent, and, if a styrene-based polymer is included, the styrene-based polymer) and the inorganic filler. This is believed to more reliably achieve high thermal conductivity.

Furthermore, when the resin composition of this embodiment contains an inorganic filler other than boron nitride, the content of the inorganic filler other than boron nitride in the resin composition is preferably 5 to 40 parts by volume, and more preferably 15 to 30 parts by volume, per 100 parts by volume of the total of the resin components (the polyphenylene ether compound, the curing agent, and, if the resin composition contains the styrene-based polymer, the styrene-based polymer) and the inorganic filler. This is believed to ensure copper foil peel strength while maintaining high thermal conductivity.

Furthermore, when the resin composition of this embodiment contains the styrene-based polymer, the content of the styrene-based polymer is preferably 5 to 25 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the total of the polyphenylene ether compound, the curing agent, and the styrene-based polymer in the resin composition.

(Other ingredients)
The resin composition according to the present embodiment may contain components other than those described above (other components) as needed, as long as the effects of the present invention are not impaired. Examples of other components contained in the resin composition according to the present embodiment include additives such as a reaction initiator, a silane coupling agent, a flame retardant, an antifoaming agent, an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, a dye or pigment, a dispersant, and a lubricant. Furthermore, the resin composition according to the present embodiment may contain, in addition to the polyphenylene ether compound, the curing agent, and the polymer, other thermosetting resins such as epoxy resins, maleimide resins, aromatic hydrocarbon resins, and aliphatic hydrocarbon resins.

As described above, the resin composition according to this embodiment may contain a reaction initiator (initiator). Even if the resin composition contains the polyphenylene ether compound, the curing agent, and the polymer, the curing reaction may proceed. However, depending on the process conditions, it may be difficult to raise the temperature high enough for curing to proceed, so a reaction initiator may be added.

The reaction initiator is not particularly limited as long as it can accelerate the curing reaction of the resin composition. Specific examples include metal oxides, azo compounds, and organic peroxides.

Specific examples of metal oxides include metal carboxylates.

Examples of organic peroxides include α,α'-di(t-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, t-butylperoxyisopropyl monocarbonate, and azobisisobutyronitrile.

Specific examples of azo compounds include 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(2-methylbutyronitrile).

Among these, preferred reaction initiators are 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide), etc. These reaction initiators have little effect on dielectric properties. In addition, because the reaction initiation temperature is relatively high, they have the advantage of being able to suppress the acceleration of the curing reaction when curing is not necessary, such as during prepreg drying, thereby preventing a decrease in the shelf life of the resin composition.

The above-mentioned reaction initiators may be used alone or in combination of two or more.

When the resin composition of this embodiment contains the reaction initiator, its content is not particularly limited, but for example, it is preferably 0.5 to 2.0 parts by mass, more preferably 0.8 to 1.5 parts by mass, and even more preferably 0.9 to 1.0 parts by mass, per 100 parts by mass of the polyphenylene ether compound, the curing agent, and the styrene-based polymer combined.

(Manufacturing method)
The method for producing the resin composition is not particularly limited, and examples thereof include a method in which the polyphenylene ether compound, the curing agent, and, if necessary, other organic components are mixed together, and then an inorganic filler is added, etc. Specifically, in the case of obtaining a varnish-like composition containing an organic solvent, the method described in the description of the prepreg below can be used.

Furthermore, by using the resin composition of this embodiment, prepregs, metal-clad laminates, wiring boards, resin-coated metal foils, and resin-coated films can be obtained as follows.

The cured product of the resin composition preferably has a thermal conductivity of 1.0 W/m·K or more and a relative dielectric constant of 4.0 or less at a frequency of 10 GHz. Thus, by using the resin composition of this embodiment, the cured product can achieve both high thermal conductivity and low dielectric properties, while also achieving high peel strength.

[Prepreg]
1 is a schematic cross-sectional view showing an example of a prepreg 1 according to an embodiment of the present invention. In the following description, the reference numerals respectively represent 1 prepreg, 2 resin composition or semi-cured resin composition, 3 fibrous substrate, 11 metal-clad laminate, 12 insulating layer, 13 metal foil, 14 wiring, 21 wiring board, 31 resin-coated metal foil, 32, 42 resin layer, 41 resin-coated film, and 43 support film.

As shown in Figure 1, the prepreg 1 according to this embodiment comprises the resin composition or a semi-cured product of the resin composition 2, and a fibrous base material 3. This prepreg 1 comprises the resin composition or a semi-cured product of the resin composition 2, and a fibrous base material 3 present in the resin composition or the semi-cured product of the resin composition 2.

In this embodiment, a semi-cured product refers to a resin composition that has been partially cured to the extent that it can be further cured. In other words, a semi-cured product is a resin composition that has been semi-cured (B-staged). For example, when a resin composition is heated, the viscosity initially gradually decreases, then curing begins, and then curing begins again, and the viscosity gradually increases. In such a case, semi-cured refers to the state between when the viscosity begins to increase and when the composition is completely cured.

The prepreg obtained using the resin composition according to this embodiment may comprise a semi-cured product of the resin composition, as described above, or may comprise the uncured resin composition itself. That is, it may be a prepreg comprising a semi-cured product of the resin composition (the resin composition in B-stage) and a fibrous base material, or a prepreg comprising the resin composition before curing (the resin composition in A-stage) and a fibrous base material. The resin composition or semi-cured product of the resin composition may be obtained by drying or heat-drying the resin composition.

When producing prepreg, resin composition 2 is often prepared in a varnish form and used to impregnate fibrous base material 3, which is the base material for forming the prepreg. That is, resin composition 2 is usually a resin varnish prepared in a varnish form. Such a varnish-like resin composition (resin varnish) is prepared, for example, as follows.

First, each component of the resin composition that is soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be performed if necessary. Then, any components that are insoluble in the organic solvent (e.g., inorganic fillers) are added as needed, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until the desired dispersion state is achieved, thereby preparing a varnish-like resin composition. The organic solvent used here is not particularly limited, as long as it dissolves the modified polyphenylene ether compound and the curing agent and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

The method for producing the prepreg is not particularly limited as long as it can produce the prepreg. Specifically, when producing the prepreg, the resin composition used in the present embodiment described above is often prepared in a varnish form and used as a resin varnish, as described above.

Specific examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. Using glass cloth results in a laminate with excellent mechanical strength, and flattened glass cloth is particularly preferred. A specific example of flattening processing is a method in which glass cloth is continuously pressed with a press roll at an appropriate pressure to compress the yarns flat. The thickness of commonly used fibrous substrates is, for example, 0.01 mm or more and 0.3 mm or less.

The method for producing the prepreg is not particularly limited, as long as it can produce the prepreg. Specifically, when producing the prepreg, the resin composition according to the present embodiment is often prepared in a varnish form, as described above, and used as a resin varnish.

Prepreg 1 can be manufactured, for example, by impregnating a fibrous substrate 3 with resin composition 2, for example, a resin composition 2 prepared in the form of a varnish, followed by drying. The resin composition 2 is impregnated into the fibrous substrate 3 by immersion, coating, or other methods. Impregnation can be repeated multiple times as needed. Furthermore, by repeating the impregnation process using multiple resin compositions with different compositions and concentrations, it is possible to adjust the final composition and impregnation amount to the desired level.

The fibrous substrate 3 impregnated with the resin composition (resin varnish) 2 is heated under the desired heating conditions, for example, at 80°C to 180°C for 1 minute to 10 minutes. This heating produces a prepreg 1 in an uncured (A-stage) or semi-cured (B-stage) state. This heating also volatilizes the organic solvent from the resin varnish, reducing or eliminating the organic solvent.

The prepreg comprising the resin composition of this embodiment or a semi-cured product of this resin composition is a prepreg that can suitably produce a cured product with low dielectric properties, high thermal conductivity, and excellent peel strength.

[Metal-clad laminate]
FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate 11 according to an embodiment of the present invention.

As shown in FIG. 2, the metal-clad laminate 11 is composed of an insulating layer 12 containing the cured product of the prepreg 1 shown in FIG. 1 and a metal foil 13 laminated together with the insulating layer 12. That is, the metal-clad laminate 11 has an insulating layer 12 containing a cured product of a resin composition and a metal foil 13 disposed on the insulating layer 12. The insulating layer 12 may be composed of either the cured product of the resin composition or the cured product of the prepreg. The thickness of the metal foil 13 varies depending on the performance required of the final wiring board and is not particularly limited. The thickness of the metal foil 13 can be appropriately set depending on the desired purpose, and is preferably 0.2 to 70 μm, for example. Examples of the metal foil 13 include copper foil and aluminum foil. When the metal foil is thin, it may be a carrier-attached copper foil equipped with a release layer and carrier to improve handling.

The method for producing the metal-clad laminate 11 is not particularly limited, as long as it can produce the metal-clad laminate 11. Specifically, a method for producing the metal-clad laminate 11 using prepreg 1 is exemplified. This method involves stacking one or more prepregs 1, then layering a metal foil 13 such as copper foil on both sides or one side of the prepreg 1, and then heat-pressing and molding the metal foil 13 and prepreg 1 to form an integrated laminate. In other words, the metal-clad laminate 11 is obtained by laminating the metal foil 13 on the prepreg 1 and then heat-pressing and molding it. The heat-pressing conditions can be appropriately set depending on the thickness of the metal-clad laminate 11 to be produced, the type of composition of the prepreg 1, and other factors. For example, the temperature can be 170 to 210°C, the pressure can be 3.5 to 4 MPa, and the time can be 60 to 150 minutes. The metal-clad laminate may also be produced without using a prepreg. For example, a method may be used in which a varnish-like resin composition is applied onto a metal foil to form a layer containing the resin composition on the metal foil, and then the layer is heated and pressed.

A metal-clad laminate having an insulating layer containing a cured product of the resin composition of this embodiment is a metal-clad laminate having an insulating layer with low dielectric properties, high thermal conductivity, and excellent peel strength.

[Wiring board]
FIG. 3 is a schematic cross-sectional view showing an example of a wiring board 21 according to an embodiment of the present invention.

As shown in Figure 3, the wiring board 21 according to this embodiment is composed of an insulating layer 12 formed by curing the prepreg 1 shown in Figure 1, and wiring 14 laminated together with the insulating layer 12 and formed by partially removing the metal foil 13. That is, the wiring board 21 has an insulating layer 12 containing a cured resin composition, and wiring 14 provided on the insulating layer 12. Furthermore, the insulating layer 12 may be made of a cured resin composition or a cured prepreg.

The method for manufacturing the wiring board 21 is not particularly limited, as long as it can be used to manufacture the wiring board 21. Specifically, examples of such methods include a method of manufacturing the wiring board 21 using the prepreg 1. Examples of such methods include a method of manufacturing the wiring board 21 by etching the metal foil 13 on the surface of the metal-clad laminate 11 manufactured as described above to form wiring, thereby manufacturing the wiring board 21 having wiring provided as a circuit on the surface of the insulating layer 12. That is, the wiring board 21 is obtained by forming a circuit by partially removing the metal foil 13 on the surface of the metal-clad laminate 11. In addition to the above methods, other methods for forming circuits include, for example, circuit formation using a semi-additive process (SAP) or a modified semi-additive process (MSAP). The wiring board 21 has an insulating layer 12 that has low dielectric properties, high heat resistance, and can favorably maintain its low dielectric properties even after a water absorption treatment.

Such wiring boards have an insulating layer with low dielectric properties, high thermal conductivity, and excellent peel strength.

[Metal foil with resin]
FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil 31 according to this embodiment.

As shown in Figure 4, the resin-coated metal foil 31 according to this embodiment comprises a resin layer 32 containing the resin composition or a semi-cured product of the resin composition, and a metal foil 13. This resin-coated metal foil 31 has the metal foil 13 on the surface of the resin layer 32. That is, this resin-coated metal foil 31 comprises the resin layer 32 and the metal foil 13 laminated together with the resin layer 32. The resin-coated metal foil 31 may also comprise another layer between the resin layer 32 and the metal foil 13.

The resin layer 32 may contain a semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-coated metal foil 31 may comprise a resin layer containing a semi-cured product of the resin composition (the resin composition in B stage) and a metal foil, or a resin layer containing the resin composition before curing (the resin composition in A stage) and a metal foil. The resin layer may contain the resin composition or a semi-cured product of the resin composition, and may or may not contain a fibrous substrate. The resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried. The fibrous substrate may be the same as the fibrous substrate of a prepreg.

The metal foil can be any metal foil used in metal-clad laminates, without limitation. Examples of metal foil include copper foil and aluminum foil.

The resin-coated metal foil 31 and the resin-coated film 41 may be provided with a cover film or the like, if necessary. The provision of a cover film can prevent the inclusion of foreign matter. The cover film is not particularly limited, but examples include polyolefin film, polyester film, polymethylpentene film, and films formed by providing a release agent layer on these films.

The method for producing the resin-coated metal foil 31 is not particularly limited, as long as it can produce the resin-coated metal foil 31. Examples of methods for producing the resin-coated metal foil 31 include a method in which the varnish-like resin composition (resin varnish) is applied to the metal foil 13 and heated. The varnish-like resin composition is applied to the metal foil 13, for example, using a bar coater. The applied resin composition is heated, for example, at a temperature of 80°C to 180°C for 1 minute to 10 minutes. The heated resin composition is formed on the metal foil 13 as an uncured resin layer 32. Note that the heating volatilizes the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

The resin-coated metal foil having a resin layer containing the resin composition of this embodiment or a semi-cured product of this resin composition is a resin-coated metal foil that can be used to preferably produce a cured product with low dielectric properties, high thermal conductivity, and excellent peel strength.

[Resin-coated film]
FIG. 5 is a schematic cross-sectional view showing an example of a resin-coated film 41 according to this embodiment.

As shown in Figure 5, the resin-coated film 41 according to this embodiment comprises a resin layer 42 containing the resin composition or a semi-cured product of the resin composition, and a support film 43. This resin-coated film 41 comprises the resin layer 42 and the support film 43 laminated together with the resin layer 42. The resin-coated film 41 may also comprise another layer between the resin layer 42 and the support film 43.

The resin layer 42 may contain a semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-coated film 41 may comprise a resin layer containing a semi-cured product of the resin composition (the resin composition in B-stage) and a support film, or a resin-coated film comprising a resin layer containing the resin composition before curing (the resin composition in A-stage) and a support film. The resin layer may or may not contain a fibrous substrate, as long as it contains the resin composition or a semi-cured product of the resin composition. The resin composition or a semi-cured product of the resin composition may be obtained by drying or heat-drying the resin composition. The fibrous substrate may be the same as the fibrous substrate of a prepreg.

The support film 43 can be any support film used for resin-coated films. Examples of such support films include electrically insulating films such as polyester film, polyethylene terephthalate (PET) film, polyimide film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, polyamide film, polycarbonate film, and polyarylate film.

The resin-coated film 41 may be provided with a cover film, etc., if necessary. By providing a cover film, it is possible to prevent the intrusion of foreign matter, etc. The cover film is not particularly limited, but examples include polyolefin film, polyester film, and polymethylpentene film.

The support film and cover film may, if necessary, have undergone surface treatments such as matte treatment, corona treatment, release treatment, and roughening treatment.

The method for producing the resin-coated film 41 is not particularly limited, as long as it can produce the resin-coated film 41. Examples of methods for producing the resin-coated film 41 include a method in which the varnish-like resin composition (resin varnish) is applied to a support film 43 and heated. The varnish-like resin composition is applied to the support film 43 using, for example, a bar coater. The applied resin composition is heated, for example, at a temperature of 80°C to 180°C for 1 minute to 10 minutes. The heated resin composition is formed on the support film 43 as an uncured resin layer 42. The heating volatilizes the organic solvent from the resin varnish, thereby reducing or eliminating the organic solvent.

A resin-coated film having a resin layer containing the resin composition according to this embodiment or a semi-cured product of this resin composition is a resin-coated film that can be used to favorably produce a cured product with low dielectric properties, high thermal conductivity, and excellent peel strength. Furthermore, it also has good formability.

The present invention will be further explained in detail below using examples, but the scope of the present invention is not limited to these examples.

[Examples 1 to 14 and Comparative Examples 1 to 3]
In the present example, each component used in preparing the resin composition will be described. The specific gravity of each component is the specific gravity when pure water is used as the reference substance.

(Polyphenylene ether compound)
PPE1: a polyphenylene ether compound having a methacryloyl group at its terminal (a modified polyphenylene ether in which the terminal hydroxyl group of polyphenylene ether is modified with a methacryloyl group; a modified polyphenylene ether compound represented by the above formula (15), in which Y in formula (15) is a dimethylmethylene group (a group represented by formula (12), in which R ₃₃ and R ₃₄ in formula (12) are methyl groups); SA9000 manufactured by SABIC Innovative Plastics, having a weight average molecular weight Mw of 2000, two terminal functional groups, and a specific gravity of 1.02).
PPE2: A modified polyphenylene ether (specific gravity: 1.04) obtained by reacting polyphenylene ether with chloromethylstyrene. Specifically, this modified polyphenylene ether was obtained by the following reaction.

First, a 1-liter three-neck flask equipped with a temperature controller, stirrer, cooling equipment, and dropping funnel was charged with 200 g of polyphenylene ether (SA90 manufactured by SABIC Innovative Plastics, two terminal hydroxyl groups, weight-average molecular weight Mw 1700), 30 g of a 50:50 mixture of p-chloromethylstyrene and m-chloromethylstyrene (chloromethylstyrene: CMS manufactured by Tokyo Chemical Industry Co., Ltd.), 1.227 g of tetra-n-butylammonium bromide as a phase transfer catalyst, and 400 g of toluene, and stirred. The mixture was then stirred until the polyphenylene ether, chloromethylstyrene, and tetra-n-butylammonium bromide were dissolved in the toluene. The mixture was gradually heated, eventually reaching a liquid temperature of 75°C. To the resulting solution, an aqueous sodium hydroxide solution (20 g sodium hydroxide/20 g water) was added dropwise over 20 minutes. The mixture was then stirred at 75°C for an additional 4 hours. Next, the contents of the flask were neutralized with 10% by mass hydrochloric acid, and a large amount of methanol was added. This caused a precipitate to form in the liquid in the flask. That is, the product contained in the reaction solution in the flask was reprecipitated. The precipitate was then filtered, washed three times with a mixture of methanol and water in a mass ratio of 80:20, and then dried under reduced pressure at 80°C for 3 hours.

The obtained solid was analyzed by ¹ H-NMR (400 MHz, CDCl ₃ , TMS). As a result of NMR measurement, a peak derived from a vinylbenzyl group (ethenylbenzyl group) was confirmed at 5 to 7 ppm. This confirmed that the obtained solid was a modified polyphenylene ether compound having a vinylbenzyl group (ethenylbenzyl group) as the substituent at the molecular terminal in the molecule. Specifically, it was confirmed that it was an ethenylbenzylated polyphenylene ether. The obtained modified polyphenylene ether compound was a modified polyphenylene ether compound represented by the above formula (14), in which Y is a dimethylmethylene group (a group represented by formula (12) in which R ₃₃ and R ₃₄ in formula (12) are methyl groups), Z is a phenylene group, R ₁ to R ₃ are hydrogen atoms, and n is 1.

In addition, the number of terminal functional groups of the modified polyphenylene ether was measured as follows.

First, the modified polyphenylene ether was accurately weighed. The weight was designated X (mg). The weighed modified polyphenylene ether was then dissolved in 25 mL of methylene chloride, and 100 μL of a 10% by weight ethanol solution of tetraethylammonium hydroxide (TEAH) (TEAH:ethanol (volume ratio) = 15:85) was added to the solution. The absorbance (Abs) at 318 nm was then measured using a UV spectrophotometer (Shimadzu Corporation, UV-1600). The number of terminal hydroxyl groups of the modified polyphenylene ether was then calculated from the measurement results using the following formula:

Residual OH amount (μmol/g) = [(25×Abs)/(ε×OPL×X)]×10 ⁶
Here, ε is the extinction coefficient and is 4700 L/mol·cm, and OPL is the cell optical path length and is 1 cm.

The calculated residual OH amount (number of terminal hydroxyl groups) of the modified polyphenylene ether was nearly zero, indicating that the hydroxyl groups of the polyphenylene ether before modification had almost completely been modified. This indicated that the decrease in the number of terminal hydroxyl groups from the polyphenylene ether before modification was the number of terminal hydroxyl groups of the polyphenylene ether before modification. In other words, the number of terminal hydroxyl groups of the polyphenylene ether before modification was found to be the number of terminal functional groups of the modified polyphenylene ether. In other words, the number of terminal functional groups was two.

The intrinsic viscosity (IV) of the modified polyphenylene ether was also measured in methylene chloride at 25°C. Specifically, the intrinsic viscosity (IV) of the modified polyphenylene ether was measured using a viscometer (AVS500 Visco System manufactured by Schott) for a 0.18 g/45 ml methylene chloride solution (liquid temperature 25°C). The resulting intrinsic viscosity (IV) of the modified polyphenylene ether was 0.086 dl/g.

The molecular weight distribution of the modified polyphenylene ether was also measured using GPC. The weight average molecular weight (Mw) was calculated from the obtained molecular weight distribution. The resulting Mw was 2,300.

(hardening agent)
TAIC: triallyl isocyanurate (TAIC manufactured by Nippon Kasei Co., Ltd.), specific gravity 1.15
DVB: Divinylbenzene (manufactured by Nippon Steel & Sumitomo Metal Corporation), specific gravity 0.91

(Reaction initiator)
Peroxide initiator: PBP (1,3-bis(butylperoxyisopropyl)benzene; Perbutyl P manufactured by NOF Corporation), specific gravity 0.91

(styrene polymer)
V9827: Hydrogenated methylstyrene (ethylene/butylene) methylstyrene copolymer (Septon V9827 manufactured by Kuraray Co., Ltd., weight average molecular weight: 92,000), specific gravity: 0.93
SIBSTAR103T: Styrene-isobutylene-styrene triblock copolymer (manufactured by Kaneka Corporation, number average molecular weight 85,000, styrene molar fraction: 30%), specific gravity 0.95

(inorganic filler)
Boron nitride 1: "AP-20S" manufactured by MARUKA Co., Ltd., volume average particle size 2.0 μm, specific gravity 2.30
Boron nitride 2: "AP-10S" manufactured by MARUKA Co., Ltd., volume average particle size 3.0 μm, specific gravity 2.30
Boron nitride 3: "MGP" manufactured by Denka Co., Ltd., volume average particle size 13 μm, specific gravity 2.30
Boron nitride 4: "SGP" manufactured by Denka Co., Ltd., volume average particle size 18 μm, specific gravity 2.30
Silica 1: "FB-7SDC" manufactured by Denka Co., Ltd., volume average particle size 5 μm, specific gravity 2.20
Silica 2: "SC2300-SVJ" manufactured by Admatechs Co., Ltd., volume average particle size 0.5 μm, specific gravity 2.20
Alumina: "DAW-03AC" manufactured by Denka Co., Ltd., volume average particle size 8 μm, specific gravity 3.92

(Preparation method)
First, each organic resin component other than the inorganic filler was added to toluene as a solvent and mixed to a solids concentration of 60 to 70% by mass in the compositions (parts by mass) shown in Tables 1 and 2. The mixture was stirred for 60 minutes. The fillers were then added to the resulting liquid in the formulations (parts by volume) shown in Tables 1 and 2, and the inorganic fillers were dispersed using a bead mill. This resulted in a varnish-like resin composition (varnish). Tables 1 and 2 also show the organic component content (parts by volume) excluding the solvent, the boron nitride content (parts by volume), and the inorganic filler content (parts by volume) other than boron nitride for each example and comparative example.

Next, the evaluation substrate (cured prepreg) was obtained as follows.

The resulting varnish was impregnated into a fibrous substrate (glass cloth: Asahi Kasei Corporation's #1078 type, L glass) and then heated and dried at 110°C for 3 minutes to produce prepregs. One, two, or four of each of the resulting prepregs were then stacked on top of each other, and copper foil (Furukawa Electric Co., Ltd.'s "FV-WS" copper foil, thickness: 35 μm) was attached to both sides. The laminate was heated to 200°C at a heating rate of 4°C/min and then heated and pressed at 200°C for 120 minutes at a pressure of 3 MPa to produce copper-clad laminates of three different thicknesses.

The copper-clad laminate prepared as described above was used as the evaluation substrate and evaluated using the methods described below. For the thermal conductivity measurements described below, a cured product of one prepreg and a copper-clad laminate of two prepregs with the copper foil removed (cured prepreg) were used. For the peel strength measurements, a copper-clad laminate of four prepregs was used. For the dielectric property (dielectric constant) evaluation test, a copper-clad laminate of four prepregs with the copper foil removed (cured prepreg) was used.

[Dielectric properties (relative permittivity)]
The dielectric constant (Dk) of the evaluation substrate (cured prepreg) at 10 GHz was measured by a cavity resonator perturbation method. Specifically, the dielectric constant of the evaluation substrate at 10 GHz was measured using a network analyzer (N5230A manufactured by Keysight Technologies, Inc.). The pass criterion in this example was set to Dk≦4.0.

[Thermal conductivity]
The thermal conductivity of the obtained evaluation substrates (cured prepreg products) was measured by a method conforming to ASTM D5470. Specifically, using a thermal property evaluation device (T3Ster DynTIM Tester manufactured by Mentor Graphics), the thermal resistance and thickness of the obtained evaluation substrates (cured products of one prepreg and cured products of two prepregs) were measured, the measured values were plotted on a graph, approximated by a straight line, and the thermal conductivity was calculated from the increase in thermal resistance and thickness. The pass criterion for thermal conductivity in this example was 1.0 W/m K or more.

[Peel strength]
First, for the peel strength (copper foil peel) test, a copper clad laminate (CCL) was produced using the prepregs of each example and comparative example. Specifically, four prepregs were stacked, and 35 μm thick copper foil (FV-WS manufactured by Furukawa Electric Co., Ltd.) was attached to both surfaces of the stack. This was then heated and pressed for 120 minutes under vacuum conditions at a temperature of 200°C and a pressure of 3 MPa to obtain a 580 μm thick copper clad laminate (CCL) (evaluation substrate) with copper foil attached to both sides.

The resulting CCL was then used to measure the peel strength of the copper foil from the insulating layer in accordance with JIS C 6481. A pattern 10 mm wide and 100 mm long was formed, and the foil was peeled off at a rate of 50 mm/min using a tensile tester, at which point the peel strength (peel strength) was measured. The measurement unit is N/mm. The pass standard for peel strength in this example was 0.40 N/mm or more.

[Particle size distribution and peaks of inorganic filler]
The particle size distribution of the inorganic filler in each of the examples and comparative examples was determined by measurement using a laser diffraction particle size distribution measuring device SALD-2100 (manufactured by Shimadzu Corporation). The specifications of the device are as follows:
Measurement method: Laser diffraction and laser scattering method Measurement range: 0.03 μm to 1000 μm
Light source: Semiconductor laser (wavelength 680 nm, output 3 mW)
Part of the study: 76-element deformed concentric sensor, side sensor, rear sensor (4 elements) for a total of 81 elements Optical sensor refractive index: 1.70-0.20i

The specifications of the batch cell used for the measurement are as follows:
External dimensions (width x depth x height): 40mm x 90mm x 14mm
Internal dimensions (width x depth x height): 36mm x 88mm x 9mm
Cell material: Quartz glass Stirring mechanism: Stirring by up and down movement of stirring plate Stirring plate material: SUS304

The particle size distribution measurement conditions are as follows.

Each measurement sample was placed in a batch cell using toluene as the dispersion solvent, and laser diffraction particle size distribution measurement was performed while stirring.

The particle size distribution was analyzed and calculated using the standard function program Wing-1 of the analysis software WingSALD included with the SALD-2100.

The peak in the particle size distribution was then determined by calculating using the volume ratio of the measured particle size distribution.

The results of each of the above evaluations are shown in Tables 1 and 2.

(Consideration)
As can be seen from Table 1, in all of the examples using the resin composition of the present invention, it was confirmed that cured products with low dielectric properties, high thermal conductivity, and excellent peel strength could be obtained. Furthermore, a comparison between Example 2 and Example 15 revealed that the inclusion of silica in addition to the boron nitride filler further improved thermal conductivity while ensuring peel strength. Furthermore, a comparison between Example 13 and Example 14 confirmed that the thermal conductivity could be further increased by having three or more peaks in the particle size distribution of the inorganic filler, each within a specific range.

On the other hand, as shown in Table 2, the samples of Comparative Examples 1 and 5, which used only relatively small particle size boron nitride, were unable to achieve sufficient peel strength. Furthermore, the samples of Comparative Examples 2 and 6, which used only relatively large particle size boron nitride, and Comparative Examples 3 and 4, which did not use boron nitride as an inorganic filler, exhibited poor thermal conductivity.

The following can be inferred from this: Small particle size boron nitride alone has good thermal conductivity but low peel strength. Boron nitride has poor adhesion to resin, so it is thought that using only small particle size boron nitride results in a large specific surface area of boron nitride, which reduces peel strength. Large particle size boron nitride alone has good peel strength but poor thermal conductivity. It is thought that when large particle size boron nitride is used, the distance between boron nitride particles increases within the resin system, resulting in poor thermal conductivity.

From the above, it was found that none of the comparative sample samples were able to achieve both thermal conductivity and peel strength.

This application is based on Japanese Patent Application No. 2020-122560, filed on July 17, 2020, the contents of which are incorporated herein by reference.

In order to express the present invention, the present invention has been properly and sufficiently described above through embodiments with reference to specific examples and drawings, etc. However, it should be recognized that those skilled in the art could easily modify and/or improve the above-described embodiments. Therefore, unless modifications or improvements made by those skilled in the art deviate from the scope of the claims set forth in the claims, such modifications or improvements are construed as being encompassed within the scope of the claims.

The present invention has wide industrial applicability in the technical fields related to electronic materials and various devices using the same.

Claims (16)

a polyphenylene ether compound;
a curing agent capable of reacting with the polyphenylene ether compound;
and an inorganic filler containing two or more types of boron nitride fillers having different volume average particle sizes ,
the content of the boron nitride filler is 15 to 30 parts by volume relative to 100 parts by volume of the total of the polyphenylene ether compound, the curing agent, and the inorganic filler;
In the particle size distribution of the inorganic filler, at least two peaks of the particle size distribution measured by a laser diffraction particle size distribution measurement method exist in a particle size range of 0.8 to 30.0 μm, and at least one peak exists in a particle size range of 0.8 to 5.0 μm and at least one peak exists in a particle size range of 5.0 to 30.0 μm. The resin composition according to claim 1, wherein the cumulative proportion of particles with particle sizes in the 0.1 to 5.0 μm range is 20 to 80%, and the cumulative proportion of particles with particle sizes in the 5.0 to 150.0 μm range is 20 to 80%, relative to the total particle size distribution of the inorganic filler (100%). The resin composition according to claim 1 or 2, wherein the polyphenylene ether compound comprises a polyphenylene ether compound having at least one of groups represented by the following formula (1) and formula (2):


(In formula (1), s represents an integer of 0 to 10, Z represents an arylene group, and _{R 1} to R ₃ each independently represent a hydrogen atom or an alkyl group.)

(In formula (2), _R4 represents a hydrogen atom or an alkyl group.) The resin composition according to any one of claims 1 to 3, wherein the curing agent comprises at least one member selected from the group consisting of polyfunctional acrylate compounds having two or more acryloyl groups in the molecule, polyfunctional methacrylate compounds having two or more methacryloyl groups in the molecule, polyfunctional vinyl compounds having two or more vinyl groups in the molecule, styrene derivatives, allyl compounds having an allyl group in the molecule, maleimide compounds having a maleimide group in the molecule, acenaphthylene compounds having an acenaphthylene structure in the molecule, and isocyanurate compounds having an isocyanurate group in the molecule. The resin composition according to any one of claims 1 to 4, wherein the inorganic filler further comprises at least one selected from the group consisting of silica, anhydrous magnesium carbonate, alumina, and silicon nitride. the inorganic filler comprises silica;
The resin composition according to claim 5, wherein the particle size distribution of the inorganic filler, as measured by a laser diffraction particle size distribution measurement method, has at least three peaks in a particle size range of 0.1 to 30.0 μm, and the peaks are at least one in a particle size range of 0.1 to 0.8 μm, at least one in a particle size range of 0.8 to 5.0 μm, and at least one in a particle size range of 5.0 to 30.0 μm. The resin composition according to any one of claims 1 to 6, wherein the content of the inorganic filler is 20 to 60 parts by volume per 100 parts by volume of the total of the polyphenylene ether compound, the curing agent, and the inorganic filler. 8. The resin composition according to claim 7, wherein the content of the inorganic filler other than the boron nitride filler is 5 to 40 parts by volume per 100 parts by volume of the total of the polyphenylene ether compound, the curing agent, and the inorganic filler. 9. The resin composition according to claim 7, wherein the content of the boron nitride filler in the inorganic filler is 25 to 80 parts by volume relative to 100 parts by volume of the inorganic filler. The resin composition according to any one of claims 1 to 9 , further comprising a styrene-based polymer. The resin composition according to any one of claims 1 to 10 , wherein a cured product of the resin composition has a thermal conductivity of 1.0 W/m·K or more and a relative dielectric constant at a frequency of 10 GHz of 4.0 or less. A prepreg comprising the resin composition according to any one of claims 1 to 11 or a semi-cured product of the resin composition and a fibrous base material. A resin-coated film comprising a resin layer containing the resin composition according to any one of claims 1 to 11 or a semi-cured product of said resin composition, and a support film. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 1 to 11 or a semi-cured product of said resin composition, and a metal foil. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 11 or a cured product of the prepreg according to claim 12 , and a metal foil. A wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 11 or a cured product of the prepreg according to claim 12 , and wiring.